Gas turbine engines, such as those which power aircraft and industrial equipment, employ a compressor to compress air that is drawn into the engine and a turbine to capture energy associated with the combustion of a fuel-air mixture. Clearances that are maintained between, e.g., rotating and static structure in the engine impact the performance and reliability of the engine. For example, in connection with the compressor, if the (radial) clearance between a blade tip and an engine case is too large there will be a loss of output performance/efficiency. On the other hand, if the clearance between the blade tip and the engine case is too small then the blade tip may rub against the engine case (or a seal disposed between the blade tip and the engine case), which may cause the components to wear over time.
The clearance is a function of various parameters. For example, materials that are used in the construction of a component impact the rate of thermal growth/expansion of that component. Components that are closer to the engine centerline tend to be exposed to elevated temperatures relative to those components located further outward or radially distant from the centerline and hence tend to experience greater degrees of growth/deflection for a given material. Still further, the operative state of the engine (or the associated aircraft, where applicable) may impact the loads that a given component experiences at a given point in time; for example, an increase in load may be experienced by a component during acceleration relative to a steady state operation.
In short, what is needed are techniques to control the degree of growth/expansion of a component under various loads (e.g., thermal loads) in order to be able to tailor a profile of a clearance over various operative states of an engine.